A system called as a thin client system is known. The thin client system is configured so that a client is provided with only a minimum function and resources such as applications and files are managed at a server side.
According to the thin client system, a client acts as if the client executes processing and holds data as a main body although a server actually makes the client display results of processing executed by the server and data held in the server.
As described above, when screen data which the client is made to display are transmitted between the server and the client, congestion occurs in a network between the server and the client, so that transmission delay may occur. This transmission delay of the network causes drawing of the screen data transmitted from the server to be delayed at the client side. Therefore, the response to operations executed at the client side deteriorates.
A dynamic encoding rate changing method for dynamically changing the encoding bit amount, sampling frequency, frame rate and the like of media stream data in conformity with a network band has been disclosed as an example of a technology for suppressing transmission delay of a network. In this dynamic encoding rate changing method, encoding control data are delivered between terminals every fixed period. For example, a terminal at the reception side receives encoding control data containing a header, a transmission time, a request sampling frequency, a request frame rate, a request bit rate and the like from a terminal at the transmission side. The terminal at the reception side generates encoding control data containing optimum frame rate and bit rate based on an analysis result of the network band analyzed by using the encoding control data, and then transmits the optimum encoding control data to the terminal at the transmission side. Thereafter, the terminal at the transmission side encodes audio data and video data in accordance with the encoding control data received from the terminal at the reception side to generate media stream data, and transmits the generated media stream data to the terminal at the reception side.    Patent Document 1: Japanese Laid-open Patent Publication No. 2004-214755
However, the thin client system has a problem that it is impossible to suppress delay of drawing on a screen at a client side without damaging operation response of the thin client as described below.
That is, it may be considered that the dynamic encoding rate changing method is applied to the thin client system to suppress the transmission delay of the network. When the network band between the server and the client narrows under the application of the dynamic encoding rate changing method, the frame rate of the screen data to be transmitted from the server to the client is uniformly reduced. This uniform reduction of the frame rate increases the update interval of the screen at the client side even when the drawing delay of the screen at the client side can be suppressed by suppressing the transmission delay of the network, so that the operation response of the thin client is deteriorated.